Mary Hannaby, from Hemel Hempstead, Hertfordshire, found the relic while on a regular six-hour Sunday detecting walks carrying the instrument with her son Michael, a 33 year-old wood carver.

The treasure had been buried four inches below the ground for around 500 years - between Ashridge and Great Gaddesden.

"You get a buzz every time you get a signal, but chances are it won't be anything," The Telegraph quoted her as saying.

Her son added: "This time, it popped up all of a sudden,You can literally miss things by inches. We couldn't believe it. We always dreamed of finding treasure."

Under the Treasure Act of 1996, finders must report potential treasure such as gold and silver objects more than 300 years old.

Finders are offered the market value for their discoveries which museums have first option to buy.

Roger Bland, head of treasure at the British Museum who thinks that the object, which at 2.8cm by 2.3cm is barely larger than a postage stamp, is an "important find" regrets the museum is short of funds to buy it.

Apparently, it is one of only three of its kind to have survived, and could be worth even more than 250,000 pounds. (ANI)